GH administration and discontinuation in healthy elderly men: effects on body composition, GH-related serum markers, resting heart rate and resting oxygen uptake
Khw. Lange et al., GH administration and discontinuation in healthy elderly men: effects on body composition, GH-related serum markers, resting heart rate and resting oxygen uptake, CLIN ENDOCR, 55(1), 2001, pp. 77-86
BACKGROUND AND OBJECTIVES GH administration results in increased lean body
mass (LBM), decreased fat mass (FM) and increased energy expenditure (EE).
GH therapy may therefore have potential benefits, especially in the elderly
, who are known to have decreased function of the GH/IGF-I axis. Several st
udies have focused on effects of GH administration in the elderly in the la
st decade. However, very limited information is available regarding changes
in body composition and EE upon GH discontinuation in the elderly. The pre
sent study therefore investigated the effects of 12 weeks of GH administrat
ion and subsequent discontinuation on body composition, resting oxygen upta
ke (VO2), resting heart rate (HR) and GH related serum markers in healthy e
lderly men.
SUBJECTS AND METHODS Sixteen healthy men [age 74 +/- 1 years (mean SEM), he
ight 174.2 +/- 1.6 cm, body weight 80.7 +/- 2.6 kg, body fat 27.5 +/- 1.1%]
completed the study protocol. Recombinant human GH (1.80 +/- 0.24 IU/day)
was administered for 12 weeks in a single-blinded, placebo-controlled desig
n. Body composition (dual energy X-ray absorptiometry), resting VO2 (indire
ct calorimetry), resting HR (telemetry) and serum IGF-I, IGF-II, IGFBP-3 an
d acid labile subunit (ALS) were measured at baseline, after 12 weeks of GH
administration and, additionally in the GH group, 1, 2, 3, 4, 5 and 9 days
after GH discontinuation.
RESULTS Body weight was unchanged from baseline to 12 weeks in both groups.
However, GH administration caused a decrease in FM (3.4 +/- 1.0 kg, P < 0.
012), paralleled by a similar increase in LBM (3.2 +/- 0.4 kg, P < 0.0002).
Resting VO2 and resting HR increased by 31 +/- 3.6% and 7.3 +/- 1.9 per mi
nute, respectively, in the GH-group, where significant increases in serum I
GF-I, IGFBP-3 and ALS also were noted. None of the above parameters changed
in the placebo group. Within 2-3 days after GH discontinuation, the GH rel
ated serum markers and resting HR returned to baseline levels, whereas rest
ing VO2 remained elevated even 9 days after GH discontinuation. In addition
, GH discontinuation caused a significant decrease in body weight (1.86 +/-
0.35 kg), derived exclusively from a decrease in LBM (1.63 +/- 0.43 kg), w
hile the decreased FM was maintained (12 weeks: 17.93 +/- 1.65 kg, +9 days:
17.74 +/- 1.62 kg).
CONCLUSIONS The increases in serum IGF-I, IGFBP-3, ALS and resting heart ra
te induced by 12 weeks of GH administration in elderly men returned to base
line levels within 2-3 days after GH discontinuation. However, resting VO2
remained elevated for a longer period. GH administration reduced fat mass b
ut maintained body weight by increasing lean body mass. In contrast, 9 days
of GH discontinuation reduced body weight exclusively by reducing lean bod
y mass.